1. Field
The present disclosure relates to the field of microfluidics and, in particular, to microfluidic devices and related methods and systems.
2. Description of Related Art
Microfluidics generally refers to the flow of fluids within microchannels. Microchannels are generally defined as channels whose dimensions are less than 1 mm and a greater than 1 μm. Above 1 mm, the fluid flow exhibits behavior that is the same as most macroscopic flows. Below 1 μm, the fluid flow may be better characterized as nanoscopic. Microfluidic flows differ from macrofluidic flows in that behaviors such as energy dissipation, surface tension, and fluidic resistance start to dominate the flow. Such characteristics of microfluidic flows are beneficial in a number of applications, such as chemical and biological analysis.
Microchannel fluidics may be provided in a printed circuit board (PCB) structure through the use of multiple layers that are fastened together. For example, U.S. Pat. No. 6,786,708, issued on Sep. 7, 2004, describes a PCB structure that consists of multiple layers of a chosen substrate or multiple types of substrates. The inner layers in the PCB structure are used as a hollow channel through which fluid can flow. Multichip module laminate technology is used to bond together the separate layers in a stack. Such PCB structures using inner layers of the PCB structure for the formation of microchannels may be referred to as “inner layer” PCB fluidic structures.
As disclosed in U.S. Pat. No. 6,786,708, the inner layers of the PCB structure are used to provide the microchannels. By photolithographic or milling operations, a section of a particular layer can be etched or machined away. Repeating this process for multiple layers and fastening the layers together in a typical laminate or PCB manufacturing process allows for the formation of multiple channels within the inner layers of the PCB structure. Holes in the outer layers of the PCB structure allow for fluids to enter and exit the channels within the PCB structure. FIG. 1 depicts fluidic channels 10 formed within a multilayer printed circuit board substrate 5. Vias 20 are used to provide fluidic or electric communication to the channels 10 buried within the multilayer substrate 5. Injection molded parts may be bonded to the PCB structure to provide for fluid ports and other such fluid handling apparatus.
While inner layer PCB microfluidic channels are constructed using well known PCB fabrication techniques, these techniques become increasing complex and expensive as additional layers are used to fabricate the microchannels. Much of the complexity and expense is due to the accurate alignment of the additional layers that must be achieved to obtain properly formed microchannels. Further, while several layers of an inner layer PCB microfluidic structure may be copper or other metal, allowing for electrical signals to be routed through the structure, components that may be used for monitoring or controlling the fluidic flow are mounted on the external layers of the PCB structure. Hence, these components cannot contact fluids that are flowing within inner layers of the structure.